This invention relates to the inhibition of the oxidation of organic compositions comprising a hydrocarbon liquid. In another aspect, this invention relates to inhibiting the oxidation of organic compositions by adding to the composition an additive which will impart the desired properties thereto. In still another aspect, the invention relates to imparting antioxidation properties to an organic composition comprising a hydrocarbon liquid without the use of an additive containing a heavy metal such as zinc. In another aspect, this invention relates to imparting anti-wear as well as antioxidation properties to an organic composition comprising a hydrocarbon liquid. In yet another aspect, this invention relates to a process for rendering a hydrocarbon liquid resistant to oxidation. In still another aspect, the invention relates to improving the anti-oxidation property of a lubricating oil, especially a lubricating oil based on mineral oil. In still another aspect, this invention relates to adding a hydrocarbylpolythiobenzoic acid to an organic composition comprising a liquid hydrocarbon, e.g. lubricating oil, in order to impart to the composition anti-oxidation properties. In another aspect, this invention relates to imparting to a lubricating oil some anti-wear as well as anti-oxidation properties by the addition of a hydrocarbylpolythiobenzoic acid. In another aspect, this invention relates to an organic composition comprising a major proportion of a hydrocarbon liquid and an oxidation-inhibiting amount of a hydrocarbylpolythiobenzoic acid. In still another aspect, this invention relates to an ashless lubricant composition comprising a lubricating oil and a hydrocarbylpolythiobenzoic acid.
For many years, a particularly effective anti-wear and anti-oxidant additive, zinc dialkyldithiophosphate (ZDTP), has been widely used. Despite the fact that this additive has been very effective and very successful in a number of lubricating motor oils, it is presently considered desirable to replace this additive with an ashless additive to reduce environmental pollution. The advent of catalytic exhaust converters on the automobile scene has precluded the use of lead compounds or other similar materials in gasolines in order to prevent premature fouling of the catalysts. Therefore, the elimination of heavy metal compounds such as zinc compounds from motor oils is also under strong consideration in order to avoid the migration of such substances through the combustion chamber and into the catalytic zone. Consequently, a substantial effort has been made to find a replacement for ZDTP which would not only be as effective but which would also be free of elements such as zinc or phosphorous.
Alkylthiobenzoic acids are known in the art as anti-corrosion agents for hydrocarbon liquids such as lubricating oils. Such compounds are disclosed in U.S. Pat. No. 3,755,176. Although alkylthiobenzoic acids can be used successfully as anti-corrosion and anti-wear additives, the anti-oxidation properties such compounds impart to a hydrocarbon liquid containing organic composition such as a lubricating oil still leaves much to be desired. Therefore, when it is desirable for an organic composition such as a lubricating composition to have anti-oxidation protection, it would be desirable to have a nonheavy metal-containing additive which can impart excellent anti-oxidation properties to the lubricating oil.
Accordingly, it is an object of this invention to provide an organic composition comprising a hydrocarbon liquid having improved anti-oxidation properties.
Another object of this invention is to provide an additive for an organic composition such as a lubricating oil in order to impart to the lubricating oil improved anti-oxidation properties.
Still another object of this invention is to provide an organic composition comprising a hydrocarbon liquid having improved anti-oxidation properties but does not contain a metal containing compound such as a zinc compound.
Yet another object of this invention is to provide a process for rendering a hydrocarbon oil resistant to oxidation.
Other objects, aspects, and the several advantages of this invention will be apparent to those skilled in the art upon a study of this disclosure and the appended claims.